1. Field of the Invention 
The present invention relates to a lubrication system for use in lubricating the interface of fifth wheel upper and lower plates. The lubrication system has particular utility in connection with the greasing of the fifth wheel plate interface when a trailer is coupled to the tractor. 
2. Description of the Prior Art 
Applying grease to the interface between the lower fifth wheel plate mounted on a tractor and the upper fifth wheel pin plate located on a trailer is extremely important to the operation, safety, and reliability of a tractor-trailer rig. This lubrication process needs to be carried out with the trailer coupled to the tractor, to avoid having to disconnect the trailer from the tractor in order to grease the fifth wheel. However, typical systems for lubricating the fifth wheel involve reservoirs of grease, which can be inconvenient and messy to use. 
The use of fifth wheel lubrication apparatus is known in the prior art. For example, U.S. Pat. No. 5,417,308 to Hartl discloses trailer fifth wheel lubrication apparatus, which forces lubricant from a reservoir, through a distribution assembly and through holes into slots on the top surface of the lower fifth wheel plate. The patent also discloses a hand-activated grease gun that can be used to supply grease to an in-line T-connector located prior to the distribution assembly. However, the Hartl '308 patent does not disclose a cartridge grease gun apparatus that can be both hand operated and/or controlled by pneumatic means for fast and clean lubrication of a fifth wheel. 
U.S. Pat. No. 6,098,754 to Toner discloses a Pneumatic greasing system for a fifth wheel that supplies grease from a reservoir to compartments beneath the lower fifth wheel plate and then forces the grease upward through orifices to the upper surface of the plate. However, the Toner '754 patent does not use a cartridge grease gun apparatus that can be hand operated and/or controlled by pneumatic means for fast and clean lubrication of the fifth wheel. 
Similarly, U.S. Pat. No. 3,743,054 to Jones discloses trailer fifth wheel lubrication that applies the lubricant from the upper fifth wheel pin plate mounted on the trailer.  However, the Jones '054 patent does not disclose the application of the lubricant to the lower fifth wheel plate. 
Lastly, U.S. Pat. Nos. 4,541,651 to Koster and 3,367,446 to Higgins may be of general interest and pertinent to the construction and design of the present invention. The Koster '651 patent uses a lubricant reservoir mounted above the upper fifth wheel pin plate to dispense the lubricant. The Higgins '446 patent discloses a motor vehicle chassis lubrication system. However, neither the Koster '651 or the Higgins '446 patents use a cartridge grease gun apparatus for lubricating the fifth wheel interface that can be hand operated or controlled pneumatic means for fast and clean lubrication of the fifth wheel. 
While the above-described devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe a fifth wheel lubrication system that uses a cartridge grease gun apparatus, which can be hand operated or controlled by pneumatic means for fast and clean lubrication of the fifth wheel. 
Therefore, a need exists for a new and improved fifth wheel lubrication system that can be used to lubricate the interface between the lower fifth wheel plate, mounted on a tractor, and the upper fifth wheel pin plate, located on a trailer. In this regard, the present invention substantially fulfills this need. In this respect, the fifth wheel lubrication system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing fast and clean lubrication of a coupled fifth wheel. 